1. Field of the Invention
The present invention relates generally to pressure regulation and self-contained breathing systems such as those used in scuba diving equipment and more specifically, to a new improved means for altering the breathing characteristics of a demand-type regulator by permitting the user to selectively adjust the venturi action in the regulator to best suit his needs during diving.
2. Prior Art
Pressure regulators such as those employed in underwater breathing apparatus, utilize the pressure differential on opposite sides of a flexible diaphragm to operate an air valve which supplies air to a breathing chamber from which the diver breathes. Typically, such a flexible diaphragm is mounted to cover an opening in the wall of the breathing chamber whereby expansion of the diaphragm actuates the air valve. More specifically, when the diver inhales while the air inlet valve is closed, the pressure in the breathing chamber is reduced causing the diaphragm to bow inwards inside the breathing chamber and thereby allowing an air inlet valve to open. When the diver exhales, pressure in the chamber increases causing the diaphragm to move out to its original condition thereby closing the air inlet valve.
Recent prior art includes disclosure of various pressure regulator structures which provide a reduction in the effort required by the diver to breath from such regulators. More specifically, regulators have been designed so that a portion of the inlet air travels into the breathing mouthpiece area in the form of a stream of air which produces a venturi effect. This venturi effect further reduces the pressures in the breathing chamber so that in effect the diver is not necessarily doing all the work required to sufficiently reduce the breathing chamber pressure to pull in and retain the diaphragm and cracking effort force setting whereby to open the air inlet valve. Thus, the venturi effect makes it easier for the diver to inhale air from the regulator. Breathing regulators which employ such venturi-type action to assist in responding to the breathing demand of the diver are highly advantageous. Unfortunately, they are not always optimally configured for the breathing requirements for each diver or for particular diving depths where ambient pressure increases as a function of depth thereby changing the parameters for the diver's degree of breathing difficulty and breathing requirements.
In response to this disadvantage of an otherwise advantageous concept, prior art patents have addressed various ways of altering venturi action in the regulator automatically during the breathing cycle. Thus, for example U.S. Pat. No. 4,214,580 to Pedersen discloses a breathing apparatus of the venturi action regulator-type hereinabove discussed which utilizes an additional moving baffle to alter the venturi effect after the diver initially inhales. However, such modification to the venturi action is accomplished automatically and internally within the regulator without any control by the diver. Thus, despite the variation in venturi action, a diver using the device disclosed in this patent would still have no manually accessible control over the venturi action during the dive.
Another prior art patent which addresses the manual control aspect of venturi-type demand regulators is disclosed in U.S. Pat. No. 4,147,176 to Christianson. This patent discloses the concept of using a conical platform in conjunction with a diaphragm wherein the diaphragm gradually flattens down against the platform to reduce the effect of sensing area during the breathing cycle. One embodiment is disclosed which has an adjustable aspirator which permits the diver to externally change the aspiration effect during the dive. Unfortunately, there is an inherent disadvantage in the manner in which the diaphragm and conical platform interact to control the venturi assist during the breathing cycle which makes the performance of the regulator substantially non-uniform during the breathing cycle. As a result, the diver may adjust the regulator characteristics to provide him with an advantageous operation for one aspect of the breathing cycle only to find that during another portion of the breathing cycle the adjustment is unsuitable.
There is, therefore, a need to provide a regulator which is of the breathing demand-type, which utilizes venturi assist to control the degree of air inlet opening, which provides the user with an external adjustment for varying the venturi effect during the dive and which, most importantly, provides either a constant or a smooth changing level of performance during the entire breathing cycle for a given adjustment setting which can still be readily varied by the diver during the dive.